Heart assist devices, systems and methods

ABSTRACT

An apparatus and method for use in assisting a human heart are disclosed. The apparatus comprises an aortic compression means which may be fully implanatable, a fluid reservoir and a pump means adapted to pump a fluid from the reservoir to the aortic compression means so as to actuate the aortic compression means at least partly in counterpulsation with the patient&#39;s heart. In addition, the device is adapted to be wholly positioned within the right chest cavity of the patient. The aortic compression means of the device may be curved along its length so as to substantially replicate the curve of the ascending aorta.

RELATED INFORMATION

This application is a continuation of U.S. application Ser. No.12/035,247 filed on Feb. 21, 2008 which is a continuation of U.S.application Ser. No. 10/786,699 filed on Feb. 24, 2004, which is acontinuation of U.S. application Ser. No. 09/869,923 filed on Oct. 15,2001. The priority of the prior application is expressly claimed, andthe disclosure of this application is hereby incorporated by referencein its entirety.

FIELD OF THE INVENTION

The present invention relates to heart assist devices, systems andmethods.

BACKGROUND OF THE INVENTION

Currently the only real options for improvement of end-stage heartfailure are medical therapy, left ventricular assist devices (LVADs) andtransplantation. ACE (Angiotensin Converting Enzyme) inhibitors unloadthe heart and prolong survival. LVADs pump blood and significantlyimprove life style and survival, but are complicated to implant,maintain and remove, with relatively high complications relating tobleeding, infection, thromboembolism, and device malfunction.

The transplant rate has stabilised at approximately 2,300 per year inthe USA, being limited by organ availability. Transplantation achieves a75% five year survival rate and a 65% ten year survival rate withsignificant improvements in functional class.

The number of people awaiting heart transplantation is steadilyincreasing and they are a sicker group, with increasing numbersrequiring hospitalisation, intravenous ionotropes, short-termpercutaneous trans-femoral intra-aortic balloon pumping and/or LVADimplantation.

The Institute of Medicine has estimated that by the year 2010, up to70,000 patients will be candidates for permanent mechanical circulatorysupport systems.

Over the last ten years, LVADs have been well proven to save lives,acting as bridges to transplantation for critically ill patients.Recently, LVADs have been considered as alternatives to transplantation,and very recently, have been explanted in a few patients who have shownrecovery. This latest realisation is starting to gather a lot ofinterest as researchers focus on recovery of the failing heart. LVADstotally unload the left ventricle and many believe that the heart willthen recover. Moreover there is evidence beyond the few patients in whomdevices have been removed that there is reversal in markers of heartfailure. On the other hand, others have described an increase inmyocardial fibrosis which raises a question of whether the heart isbeing unloaded too much.

The intra-aortic balloon pump (IABP) was first proposed ill the 1960s asa method of partial support for the acutely failing heart, for example,after heart surgery or heart attack. It was built as a long thincatheter [10-14 Fr] with an elongated balloon at its tip [volume 30-40ml]. The balloon was inserted via the femoral artery and inflated anddeflated in counter-pulsation with the heart beat. Inflation in diastolecauses a diastolic pressure augmentation and increases coronary arteryblood flow and deflating in systole (triggered by the R wave of the ECG)reduces the afterload, or the pressure head against which the leftventricle has to eject blood. Early investigators determined that thebest and most efficient balloon position was closest to the heart, i.e.,in the ascending aorta. However, in recent times, the balloon ispositioned via the femoral artery in the descending aorta for short term(1-10 days) use. There is substantial proof beyond doubt thatcounterpulsation works very well in the short-term to assist hearts torecover when drugs (ionotropes etc.) are insufficient or inappropriateto support the cardiovascular system.

Intra-aortic balloon heart pumps operating in counterpulsation assistthe heart function. When inflated, the balloon propels bloodperipherally from within the aorta to improve blood circulation in thepatient. Moreover, more blood is forced into the coronary arteries tohelp nourish and strengthen the heart muscle. However, the balloon comesinto direct contact with the blood flowing into the aorta, which cancause damage to the blood cells and there is a risk of thromboembolism.In addition, current intra-aortic balloon pump systems are inflated bymeans of a tube passing through the body, the tube connecting theballoon to an external compressor. The opening for the tube to enter thebody provides a possible site of infection or other injury. The tube istypically inserted into a groin vessel, the femoral artery, and there isa high risk of associated leg complications. Further, the patient isbedridden and cannot mobilize. Additionally, the use of a gas to inflatethe balloon is not an entirely safe operation since any leakage of gasfrom the balloon into the blood stream could cause an air embolus.

Aortic compression (periaortic diastolic compression) has been describedas a means to increase coronary blood flow. For example, U.S. Pat. No.4,583,523 describes an implantable heart assist device including anelongated assembly extending transversely between the ribs of a patientfrom the rib cage to the aorta of the heart to be assisted. The assemblyincludes an aorta compressing device at the front end and a mountingdevice at the rear end thereof to support the device from the ribs ofthe patient. A motive device actuates and deactivates the compressingdevice alternatively to help pump blood through the aorta in acounterpulsation mode of operation. Although this device has advantagesfor many applications, it does require relatively complicated surgery toimplant/explant the device, particularly in regard to the need to mountthe device including its motive means, to the ribs of the patient.Moreover the mounting arrangement and motive means of the device have tobe positioned outside the rib cage, making the presence of the devicemore noticeable to the patient. There is also substantial risk ofinfection With the device coming through the skin. Furthermore, becausethe device is attached/mounted to the ribs, there may be shear stresseson the aorta as the rib cage moves with inspiration/expiration. Thesestresses may cause untoward damage of the aorta.

U.S. Pat. No. 4,979,936 discloses an autologous biologic pump in theform of an apparatus using skeletal muscle formed into a pouch whichthen surrounds a collapsible, shape-retaining bladder. The bladder isconnected to a second bladder enclosed in a sheath around a portion ofthe aorta. The bladders are filled with a fluid such that when theskeletal muscle contracts in response to an electrical stimulation, thefluid is forced from the first bladder into the second bladder sheathedaround the aorta, expanding that second bladder and forcing the aorta tocompress. Although this approach may be useful in some circumstances, itis doubtful that it is suitable for long term in that the musclefunction would probably degrade over time. Furthermore, the muscle hasto be “trained” for many weeks before the device can be relied on toassist blood circulation.

WO 99/04833 discloses a cardiac ventricle aid device which is implantedin the abdominal cavity with an aorta sleeve tube placed on, or insertedin, the descending aorta. A disadvantage of the disclosed device is ithas a separate actuator and compliance chamber and its implantation isthus complicated. Another disadvantage is it is difficult to securelymount the device components to a structure in the abdominal cavity thatis capable of supporting its weight. A further disadvantage is a numberof vertebral arteries stem from the descending aorta which can bedamaged during the implantation of the device.

It would be desirable to have a heart assist device that could bequickly and totally implanted in a relatively easy manner and withminimum trauma to the patient and to allow ambulation with low risk ofcomplications. Also desirable would be a heart assist device that allowspartial unloading of the heart longterm, augmenting the cardiac outputof the native heart, and possibly allowing substantial recovery of theheart so that the device could be weaned. Moreover, it would bedesirable for such a device to have no blood contacting surfaces, andnot require cardiopulmonary bypass to implant the device. In a smallproportion of patients however there will exist aortic disease making aperiaortic device unsuitable. In these patients it would be desirable tobe able to apply the same aortic counterpulsation, but with a devicethat replaces the ascending aorta. Such a device would requirecardiopulmonary bypass and would be blood contacting, but has the sameadvantages of allowing partial unloading of the heart longterm,augmenting the cardiac output of the native heart, and possibly allowingsubstantial recovery of the heart so that the device could be weaned.

It is an object of the present invention to satisfy one or more of theabove desirable criteria.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a heart assist deviceadapted for implantation into a patient, the device including

a) an aortic compression means adapted, when actuated, to compress anaorta of a patient;

b) a fluid reservoir; and

c) a pump means adapted to pump a fluid from the fluid reservoir to theaortic compression means so as to actuate the aortic compression meansat least partly in counterpulsation with the patient's heart,

wherein the fluid reservoir is adapted to be wholly positioned withinthe chest is cavity of the patient.

In a second aspect, the present invention provides a heart assist deviceadapted for implantation into a patient the device including:

a) an aortic compression means adapted, when actuated, to compress theascending aorta of a patient;

b) a liquid reservoir;

c) a pump means adapted to pump a liquid from the liquid reservoir tothe aortic compression means so as to actuate the compression means,wherein the liquid reservoir and the aortic compression means areadapted to be positioned in close juxtaposition with one another withinthe chest cavity of the patient.

In a third aspect, the present invention provides an aortic compressionmeans for use in a heart assist device, the aortic compression meansincluding:

a) an elastic inflatable cuff adapted to be placed about the ascendingaorta of a patient; and

b) a flexible, substantially inelastic, sheath adapted to extend aroundthe cuff and at least assist in retaining it in position on the aorta.

In a fourth aspect the present invention provides a heart assist deviceincluding:

a) an aortic compression means adapted to be placed around the ascendingaorta of a patient; and

b) an actuation means to periodically actuate the aortic compressionmeans in at least partial counterpulsation with the heart,

wherein the aortic compression means and the actuation means are placedwholly within the chest activity of the patient.

In a fifth aspect, the present invention provides a heart assist deviceadapted for implantation wholly into a bodily cavity of a patient thedevice including:

a) an aortic compression means adapted, when actuated, to compress anaorta of a patient;

b) a housing with an exterior surface;

c) a fluid reservoir in the housing, the fluid reservoir having aflexible exterior surface forming part of the housing exterior surface;and

d) a pump means adapted to pump a fluid from the fluid reservoir to theaortic compression means so as to actuate the aortic compression meansat least partly in counterpulsation with the patient's heart,

wherein the fluid reservoir flexible exterior surface is adapted toexpand during aortic compression and constrict in the absence of aorticcompression and is further adapted to be positioned substantiallyadjacent a flexible organ in the patient's bodily cavity.

Preferably, the bodily cavity is the thoracic cavity and the organ isthe lung.

In a sixth aspect the present invention provides a heart assist deviceadapted for implantation into a patient, the device including:

a) an elastic inflatable cuff adapted, when inflated, to compress anaorta of a patient;

b) a fluid reservoir;

c) a means for pumping a fluid from the fluid reservoir to the cuff soas to inflate the aortic compression means at least partly incounterpulsation with the patient's heart; and

d) a means for adjusting the volume of fluid in the cuff in the absenceof aortic compression.

In a seventh aspect, the present invention provides a human or animalhaving a heart assist device according to any one of the precedingaspects of the invention implanted therein.

In a further aspect, the present invention provides an implantablesystem for assisting the functioning of the heart of a subject, thesystem including:

an implantable device for assisting the functioning of the heart of asubject, including:

means for externally engaging and compressing the aorta;

motive means responsive to control signal(s) for actuating anddeactivating the compressing means cyclically to help blood pump throughthe aorta, wherein the compressing means and the motive means are fullyimplantable within the thoracic cavity of the subject and wherein thecompressing means and/or motive means include means to adapted forattachment to the aorta and/or surrounding tissue within the thoraciccavity of the subject;

sensing means adapted for sensing the heart and generating sensingsignals;

control means responsive to the sensing signals for generating thecontrol signal(s); and

a power source for providing power to the motive means.

The device of the invention may operate in countersynchronisation to theheart (counterpulsation).

An advantage of the device and system of the present invention is thatthe risk of limb ischemia associated with conventional IAB systems isavoided because there is no blood contact with the device whatsoever.Patient ambulation is also possible. Additionally the implantationtechnique used for the device of the invention is less invasive thanthose required for other devices. In particular, compared to thearrangement taught in U.S. Pat. No. 4,583,523, the device of the presentinvention provides a better outcome in term of reduced risk ofinfection, cosmesis and ease of implant and explant. A further advantageof the device and system of the present invention is that there islittle risk to die patient in the event of device failure. The devicehas the great advantage of being able to be weaned and turned off in theevent of cardiac recovery. This is simply not possible with known LVADs.Furthermore if the heart shows signs of relapsing back into failure, thedevice can be switched back on.

The compressing means of the device of the present invention preferablyincludes a preshaped balloon cuff for wrapping around a portion of theaorta. Preferably, the balloon is configured longitudinally to fit thecurve, that of a circular or oval arc, of the ascending aorta. In aparticularly preferred form of the device of the present invention, thecross-section of the cuff is C-shaped, allowing wrapping of the cuffwith some overlap around the aorta. Preferably, the cuff is shaped suchthat it does concentrically compress the length of enclosed aorta andspreads the compression forces evenly, reducing any wear or fatigue onany one part of the aorta. The balloon cuff is enclosed within aflexible and non-elastic outer sleeve. The sleeve has an elongated“tongue” on one arm of the C-shaped cuff and this is passed around theaorta to be secured by suturing or other means on the outer aspect ofthe other arm of the C-shaped cuff. This arrangement stops the ballooninflation force from going outwards. Furthermore, the preshaped cuff andflexible sleeve arc particularly designed to create a snug fit and lowprofile on the aorta, to reduce damage to the aorta and surroundingstructures, and to create maximum efficiency of the device.

In a preferred form of the invention, the device is adapted forcompression of the ascending aorta. An upper mid-line sternotomyprovides easy surgical access to the ascending aorta and has the furtheradvantage of not being very painful for the patient. A minimum incisionis required in this procedure. In this mode of use of the device of theinvention, the compressing means is preferably adapted to squeezeapproximately 15-25 ml of blood from the ascending aorta in eachcompression cycle.

The cuff has a single inlet/outlet port for the fluid to move toinflate/deflate the balloon. The fluid used is preferably liquid, suchas water or saline, as this is noncompressible and less likely to leakcompared to gas. Furthermore, using a liquid allows a fully implantabledevice so that the patient can mobilize easily. The port and connectingtube to the motive means is of sufficient diameter and length to allowrapid emptying and filling of the cuff without generating too highcompression pressures. The fluid must move within 0.15 sec for effectivecounterpulsation action. The compressive force emptying the cuff is theforce exerted by the compressed aorta. This approximately 100 mmHg. Atube lumen of approximately 1 to 1.5 cm with a length of 3 to 8 cmallows 17 to 25 ml fluid to pass down a gradient of 100 mmHg in lessthan 0.15 sec. The compressive force filling the cuff is generated bythe motive means, and this pressure gradient is approximately the sameie the motive means generates approximately 200 mmHg to allow the fluidto shift into the cuff in less than 0.15 sec.

The port more preferably has a trumpet-shaped or flanged opening intothe cuff to spread the fluid more evenly into the balloon duringinflation and to assist more rapid deflation. There may be a diffusermounted within the lumen of the port to reduce the fluid force on theballoon cuff during inflation.

Preferably, the motive means drives the fluid via a fluid filled saccontained within the motive means. The motive means of the device of theinvention may be any means that is capable of cyclically compressing anddecompressing the fluid sac. The motive means may be a mechanical or anelectromechanical device. The motive means may be an electric motor/camarrangement. The motive means may include spring mounted arms driven bya pulse of power to hinged solenoids or the like to drive the pressureplates towards each other and thereby compress the aorta. An example ofa suitable motive means is an adaptation of the solenoid actuatordescribed in U.S. Pat. No. 4,457,673, the relevant disclosure of whichis incorporated herein by reference. The motive means may also be basedon that used in the Novacor N100 Left Ventricular Assist System.

The motive means is preferably enclosed in an air-tight housing. Thehousing may have a flexible portion that allows for the fluid shift fromthe motive means—the flexible portion is presented toward the lungtissue and can thus move back and forth. More particularly the motivemeans is fully implanted within the thoracic cavity and a pressurecompliance membrane “interfaces” with the lung surface. Alternativelythe housing may be rigid and when the motive means is activated and thefluid sac compressed, a small vacuum is created within the housing. Thisvacuum has the advantage of increasing the pressure gradient forsubsequent emptying of the cuff, to make emptying more rapid. The levelof vacuum could be adjusted by accessing a transcutaneous gas reservoirlinked to the housing. A final alternative is to have a external gasline from the motive means to allow gas exhaust, eliminating the needfor a compliance chamber, but introducing a percutaneous line that hasan increased risk of infection.

The motive means may be designed so that in the event of failure, itautomatically goes into “off” with the fluid sac filled so that theaorta is not compressed, thus minimising risk to the patient.

The motive means may include or be associated with means for detectingspeed and completeness of cuff filling and emptying, and of monitoringthe fluid pressure within the connector tube, means for measuringarterial blood pressure or flow. The motive means may also act to recordthe ECG, having electrodes positioned on the housing or as separatewires attached to body tissues.

The means adapted for attachment to the aorta and/or surrounding tissueof the subject may be any suitable means. For example, the attachmentmeans may be adapted for suturing and/or gluing the compressing means ormotive means to the aorta or the surrounding tissue within the chestcavity. The attachment means may be suturing tabs. The attachment meansmay be apertures allowing ingrowth of tissue and/or surface portionsadapted to promote tissue growth into or onto the compressing meansand/or the motive means so as to hold the device in position relative tothe aorta. For example, the cuff may have a plurality of holes throughwhich the cuff may be sutured to the aorta. The cuff may also have holeor slits to accommodate coronary artery bypass grafts to the ascendingaorta. The motive means will sit within the chest cavity, preferably theright thoracic cavity, between the mediastinum and the right lung.

The sensor means may be means detecting a selected physiological eventassociated with heartbeat. The sensor means may be any means forproducing an ECG. Means for detecting the action potentials of thecardiac muscles, for example electrodes, are well known to those skilledin the art and will not be described in detail here.

The control means may be any means capable of providing an output toactuate the motive means in response to signal(s) providing the sensormeans.

The control means may provide signals to the motor means tocountersynchronise compression of the aorta with the heart beat toprovide counterpulsation, for example, aorta compression may commencewith aortic valve closure (ventricular diastole), whilst aorta releaseoccurs just prior to contraction/ejection (ventricular systole).

The power means may be an internal and/or external battery, or TET(transcutaneous electronic transfer).

De-activation of the compressing means may be timed to the R wave of theECG and may be adapted for adjustment either manually or automatically.The dicrotic notch on the arterial pressure wave may provide the signalfor actuation of the compressing means.

In yet a further aspect, the present invention provides a method forimproving blood circulation in a subject, the method includingimplanting a device in accordance with the invention fully within thethoracic cavity of a subject, actuating the compressing meansperiodically in synchrony with the diastole period to compress theaorta; and alternating the period of actuation with periods ofdeactivation of the compressing means thereby allowing the aorta toreturn to its uncompressed shape.

The system and device of the invention allow relief/recovery fromchronic heart failure whilst allowing the subject to move around freelywithout being constrained by a large external pumping device.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described, by way ofexamples only, with reference to the accompanying drawings in which:

FIG. 1 a is a schematic drawing of a first embodiment of a heart assistdevice according to the invention implanted in the thoracic cavity of asubject;

FIG. 1 b is an enlarged view of the device shown in FIG. 1 a;

FIG. 2 a is an enlarged perspective detailed view of the device shown inFIG. 1 a;

FIG. 2 b is a partial top view of the device shown in FIG. 1 a;

FIG. 3 is top view of a second embodiment of a heart assist deviceaccording to the invention;

FIG. 4 is a top view of a third embodiment of a heart assist deviceaccording to the invention;

FIG. 5 a is a top view of a fourth embodiment of a heart assist deviceaccording to the invention;

FIG. 5 b is a perspective view of the device shown in FIG. 5 a;

FIG. 6 is a block diagram of an embodiment of a cardiac assist systemaccording to the invention;

FIG. 7 is a side view of an embodiment of an inflatable cuff;

FIG. 8 is a rear view of the cuff shown in FIG. 7;

FIG. 9 a is a top view of the cuff shown in FIG. 7;

FIG. 9 b is a top view of the cuff shown in FIG. 7 after application ofan external sheath;

FIG. 10 is a front view of the cuff shown in FIG. 7;

FIG. 11 is a fifth embodiment of a heart assist device according to theinvention;

FIG. 12 is a schematic side view of a sixth embodiment of a heart assistdevice according to the invention;

FIG. 13 is a schematic side view of an seventh embodiment of a heartassist device according to the invention;

FIG. 14 is an indication of an electrical cardiograph (ECG) readout,heart diastolic pressure (Pr.) and power supply (Po) for the deviceshown in FIG. 13;

FIG. 15 is a schematic side view of an eighth embodiment of a heartassist device according to the invention;

FIG. 16 is an exploded view of the pump housing of the device shown inFIG. 15;

FIG. 17 is a schematic cross sectional view of a ninth embodiment of aheart assist device according to the invention; and

FIG. 18 is a schematic view of a tenth embodiment of a heart assistdevice according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 a to 2 b are schematic drawings showings a first embodiment of aheart assist device 10 in accordance with the invention. The device 10is suitable for complete implantation in the thoracic cavity of asubject 99 adjacent the ascending portion of the aorta 15, as shown. Thedevice 10 includes an aortic compression means in the form of a hingedsolenoid 2 (see FIGS. 2 a and 2 b) in a housing 12. The solenoid 2 isdriven by pulses of electrical power from a controller/battery 14 toactuate wedge-shaped compression plates 4 via arms 3. The wedge-shapedplates 4 surround the ascending portion of the aorta 15. When the plates4 are actuated they approach each other and that part of the aorta 15between the plates 4 is compressed. The plates 4 have a plurality ofholes 6 that provide means for suturing the plates to the aorta 15 andpermitting ingrowth of tissue therethrough.

FIGS. 2 a and 2 b are detailed schematic drawings of the solenoid 2which show that it includes two arcuate plates 26 hinged at 8. Theplates 26 are shown in the de-activated (resting) position in FIG. 2 aand are shown in the actuated position in FIG. 2 b compressing the aorta15. The plates 26 are soft form moulded and are actuated by the hingedsolenoid 4 via arms 23.

FIGS. 3 to 5 b are schematic drawings of second to fourth embodiments ofheart assist devices in accordance with the present invention.

In the second embodiment shown in FIG. 3, the compression plates 34 areactuated via arms 33, with each of the arms 33 being acted on by arespective rod solenoid 38 acting through springs 37 between the rodsolenoid 38 and the respective arm 33.

In the third embodiment shown in FIG. 4, solenoids 48 act on deformablenitinol plates 44 connected together at either end 47 to encircle theaorta 15.

In the fourth embodiment shown in FIGS. 5 a and 5 b, wedge-shaped plates54 are connected together at one end 57 and each plate is actuated bysolenoids 58 acting through arms 53. As best shown in FIG. 5 b, thewedge-shaped plates 54 effectively conform to the shape of the ascendingaorta 15.

FIG. 6 is a block diagram of an embodiment of a cardiac assist systemconstructed in accordance with the invention suitable for use with, forexample, the cardiac assist device 10.

Initiation of the compression of the aorta 15 by the compression plates4 is accomplished by energisation of the solenoid 2. This energisationis under the control of a control means 100 which activates the solenoid2 of the motive means 1 in response to signals received from an ECGmonitor 102 or systemic arterial blood pressure 103 or the like. The ECGmonitor 102 and/or the control means 1 are preferably implanted but maybe on the body of the subject 99.

In operation, de-activation of the compression plates 4 draws them apartand effectively unloads the left ventricle by allowing the aorta 15 toreturn to its usual circular shape. The expansion of the aorta 15between the de-activated plates causes a pressure drop in the aorta 15,facilitating left ventricle ejection (ie unloading of the heart). Afterthe heart has finished ejecting blood into the aorta 15 and the aorticvalve closes, the plates 4 are activated to move them towards each otherand compress the aorta 15 and thereby squeeze blood out of the volume ofthe aorta 15 compressed by the compression plates 4 and augment thediastolic pressure. Coronary artery blood flow to the left ventricleoccurs predominantly in diastole so compression of the aorta 11 alsoaugments coronary blood flow.

FIGS. 7 to 10 show an aortic compression means in the form of a flexiblehollow inflatable cuff 60. The cuff 60 is curved along its length so asto substantially replicate the curve of the aorta 15 adjacent thereto.The cuff 60 is shown in its de-activated (uninflated) state in FIG. 9 a,and has two free ends 61 and 62 which are adapted to overlap when thecuff 60 is placed around the aorta. As best shown in FIG. 10, the cuff60 is retained adjacent the aorta after implantation by suturing the twofree ends together at 63. This also ensures that the cuff 60 is a snugfit around the aorta, when the aorta is in its usual circular shape.

Further, as best shown in FIG. 9 b, a substantially inelastic, flexiblesheath 65 is also preferably placed around the cuff 60. The sheath 65assists in retaining the cuff 60 adjacent the aorta and inwardlyconcentrates the compression forces generated by inflation of the cuff60, as indicated by arrows 66. The sheath 65 can also have free endssutured together to retain it and the cuff 60 adjacent the aorta inaddition to, or in place of, the cuff sutures 63. The sheath 65 ispreferably made from DACRON (Trade Mark), KEVLAR (Trade Mark), TEFLON(Trade Mari), GORE-TEX (Trade Mark), polyurethane or other flexibleinelastic bio-compatible materials. The sheath 65 is preferably glued,fused or otherwise bonded to the cuff 60.

The cuff 60 also has a single inlet/outlet port 64 for the introductionof fluid to inflate the cuff 60 and thereby compress the aorta and theremoval of fluid for the deflation of the cuff and relaxing of theaorta. The fluid is preferably water or an isotonic solution of salt orother low-viscosity, non-toxic liquid.

The fluid is actively pumped into the cuff 60 for inflation into theshape indicated in phantom in FIG. 9 b. The cuff 60 can be activelydeflated by suctioning the fluid from the cuff 60. Alternatively, thecuff 60 can be passively deflated by the blood pressure of theconstricted aorta re-expanding and returning the cuff 60 to the stateshown in FIG. 9 a, which ejects the fluid from the cuff 60. It ispreferable to actively deflate the cuff 60 as it gives betterpresystolic unloading of the heart and counteracts any highintrathoracic pressures, such as when the subject coughs. In eithercase, the natural resilience of the cuff 60 also assists in deflation bybiasing the cuff 60 to the shape shown in FIG. 9 b.

In another embodiment of heart assist device (not shown), thecompression plates 4 are used to squeeze the cuff 60. This embodimentcan be configured to operate in two ways. Firstly, the plates 4 canprovide a larger aortic compression and the cuff 60 a smaller aorticcompression, either simultaneously or one after the other. This reducesthe fluid requirements of the cuff 60. Secondly, the cuff 60 can be setat a fixed inflation and provide a cushion between the plates 4 and theaorta.

In other embodiments of cuff (not shown), the sheath is integrallyformed with the cuff, preferably by moulding, or in the form offlexible, inelastic fibres embedded in the cuff.

FIGS. 11 to 18 are schematic drawings of fifth to tenth embodiments ofheart assist devices in accordance with the present invention thatutilise the cuff 60 shown in FIGS. 7 to 10.

In the fifth embodiment shown in FIG. 11, the cuff 60 is closely coupledto a fluid-filled air-tight housing 70 that has therein a pump, in theform of rotatable impeller 71 and a pair of valves 72 and 73 fordirecting the flow of the impeller 71. The housing also includes aninlet/outlet 76 in fluid communication with the inlet/outlet port 64 ofthe cuff 60. A fluid reservoir is also provided in the housing 70 in theform of an internal portion 74 of the volume of the housing 70, as is apressure compliance means, in the form of a substantially flexibleportion of 75 of the housing 70.

In operation, energisation of the impeller 71 with the valves 72 and 73in the position shown in FIG. 11 causes fluid to be actively withdrawnfrom the cuff 60, which allow the aorta to return to its usual circularshape. This fluid is pumped into the internal portion 74 of the housing70 and causes the flexible portion 75 to expand to the position shown inFIG. 11. When the valves 71 and 73 are in the positions shown in phantomin FIG. 11 and the impeller 71 is energised, the fluid in the portion 74is pumped into the cuff 60 to expand same and to compress the aorta. Theremoval of fluid from the portion 74 causes the flexible portion 75 toretract to the position shown in the phantom in FIG. 11. As with earlierembodiments, the control of the impeller and valves is in response tosignals received from an ECG monitor or systemic arterial blood pressureor the like.

In the sixth embodiment shown in FIG. 12, the device has only a singlevalve 76. The aorta is compressed by positioning the valve 76 as shownin FIG. 12 and energising the impeller 71. When the valve 76 is moved tothe position shown in phantom in FIG. 2 and impeller is de-energised theexpanding aorta passively ejects the fluid back into the portion 74 ofthe housing 71 and causes the flexible portion 75 to expand to theposition shown in phantom.

In the seventh embodiment shown in FIG. 13, the impeller 71 is driven inone direction to cause fluid flow in the direction indicated by thearrow to deflate the cuff 60 and expand the flexible portion 75.Reversing the direction of the impeller 71 causes the flexible portion75 to retract to the position shown in phantom as fluid is displacedinto the cuff 60 to inflate same. This embodiment requires variablepower control to the motor driving the impeller 71 and a plot of themotor power requirements (Po) relative to the subject's electrocardiograph reading (ECG) and aortic pressure (Pr.) are shown in FIG.14.

In the eighth embodiment shown in FIGS. 15 and 16, the housing 71 has arigid upper portion 71 a and a partially rigid lower portion 71 b thatincludes the flexible portion 75. A motor 77 is mounted in the lowerportion 71 b that drives a pair of rollers 78, each positioned on an endof a common shaft 79. The housing portion 71 b also has a pair ofupstanding guide posts 80 which are slidably received in correspondingholes in a swash plate 81. The swash plate 81 has a pair of camformations 82 on its underside. A fluid-filled sac 83 is positionedbetween the swash plate 81 and the housing portion 71 a . The interiorof the sac 83 is in fluid communication with the interior of the cuff60. Power is supplied to the motor 77 through line 84.

In operation, the motor 77 is energised to rotate the rollers 78, whichride along the cam formations 82 to drive the swash plate 81 upwards tocompress the sac 83 and eject the fluid therein into the cuff 60 toinflate same. When the rollers 78 have passed the cams 82 the swashplate 81 returns to its original position and the expanding aortapassively ejects the fluid back into the sac 83. In an alternativeembodiment (not shown), the rollers 78 are linked to the earn formations82 to drive the swash plate 81 up and down and thereby actively inflateand actively deflate the cuff 60. As a further alternative, (not shown)a stepper motor(s) can be used to drive the swash plate.

In the ninth embodiment shown in FIG. 17, the housing 71 has a fluidfilled sac 83 positioned between a pair of compression plates 84 whichare hinged at 85 and driven by a solenoid 86. Energising the solenoid 86brines the plates 84 together to squeeze the sac 83 and force the liquidtherein into the cuff 60 to inflate same. De-energising the solenoid 86draws the plates 84 apart and the expanding aorta passively ejects thefluid back into the sac 83. As with earlier embodiments as the sac 83inflates the flexible portion 75 of the housing 71 expands toaccommodate the increase in pressure in the housing 71.

In the tenth embodiment shown in FIG. 18, the heart assist deviceincludes a liquid pressure adjustment means, in the form of remotereservoir 90, connected between the cuff 60 and the reservoir 74. Liquidcan be added to the heart assist device, via the remote reservoir 90, toadjust the liquid retained in the (de-activated) cuff 60 and therebyadjust the pressure therein. This allows the size of the cuff 60 to beadjusted to compensate for changes in the size of the aorta and/or theamount of aortic compression to be adjusted to, for example, wean thepatient from the heart assist device. When the reservoir is positionednear the skin, its volume can be adjusted by using a needle to inject orwithdraw liquid. When the reservoir is positioned near the heart assistdevice, its volume can be adjusted by adding or withdrawing liquid via atranscutaneous tube. The pressure in the reservoir 90 can also be sensedand automatically adjusted so as to maintain a predetermined pressure.

It will be appreciated that the system and device of the presentinvention, in their preferred forms, are designed to be simple with noblood contact and a much lower morbidity risk compared to LVADs. Thedevice and system allows the heart to remain totally un-instrumented,and the device, by effective counterpulsation in the aorta, augments thecardiac output up to 15-20%. All natural blood pathways are maintained.Pulsatile blood flow is also maintained. The patient is able to ambulateand there is no risk of leg ischaemia.

The present invention provides for long term relief and/orstabilization/of or recovery from chronic heart failure. Moreover thepresent invention may be a suitable bridging device for transplantation.

The device and system of the above-described embodiments improve cardiacwork efficiency by reducing the afterload (pressure/resistance to flowwhich the heart has to overcome to eject blood) during systole (ejectionphase), by augmenting diastolic aortic blood pressure to maintain agreater mean arterial pressure, and by increasing left ventricularcoronary artery blood flow during diastole.

The preferred embodiments of the heart assist device compress theascending aorta. This is advantageous as the ascending aorta is lessprone to disease than the descending aorta and, being closer to theheart, provides improved pumping efficiency and thus a smaller heartassist device.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the invention as shown inthe specific embodiments without departing from the spirit or scope ofthe invention as broadly described. For example, although the inventionhas been described in specific reference to compression of the aorta,the devices, systems and methods of the present invention can equally beused for the compression of the pulmonary artery to effectively act as aright ventrical assist device, and the present invention extends to thisalternative aspect. The present embodiments are, therefore, to beconsidered in all respects as illustrative and not restrictive.

1. In a heart assist device adapted to be implanted into a patient, theimprovement comprising: a) an aortic compression means adapted to beplaced so that, when actuated, it will compress the ascending aorta ofthe patient; b) a fluid reservoir; and c) an electrically powered pumpmeans arranged to pump a fluid from the fluid reservoir to the aorticcompression means so as to actuate the aortic compression means at leastin counterpulsation with the patient's heart, wherein the fluidreservoir and the pump means are wholly positioned within the rightchest of the patient.